
//给你单链表的头节点head请你反转链表,并返回反转后的链表。
struct ListNode* reverseList(struct ListNode* head)
{
    if (head == NULL || head->next == NULL)
        return head;
    struct ListNode* n1 = NULL, * n2 = head, * n3 = head->next;
    while (n2)
    {
        n2->next = n1;
        n1 = n2;
        n2 = n3;
        if (n3)
        {
            n3 = n3->next;
        }
    }
    return n1;
}
struct ListNode* reverseList(struct ListNode* head)
{
    struct ListNode* newNode = NULL;
    struct ListNode* cru = head;

    while (cru)
    {
        struct ListNode* NEXT = cru->next;
        cru->next = newNode;
        newNode = cru;
        cru = NEXT;
    }
    return newNode;
}